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dir.c

/*
 *  linux/fs/fat/dir.c
 *
 *  directory handling functions for fat-based filesystems
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
 *
 *  VFAT extensions by Gordon Chaffee <chaffee@plateau.cs.berkeley.edu>
 *  Merged with msdos fs by Henrik Storner <storner@osiris.ping.dk>
 *  Rewritten for constant inumbers. Plugged buffer overrun in readdir(). AV
 *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/msdos_fs.h>
#include <linux/dirent.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
#include <linux/compat.h>
#include <asm/uaccess.h>

static inline loff_t fat_make_i_pos(struct super_block *sb,
                            struct buffer_head *bh,
                            struct msdos_dir_entry *de)
{
      return ((loff_t)bh->b_blocknr << MSDOS_SB(sb)->dir_per_block_bits)
            | (de - (struct msdos_dir_entry *)bh->b_data);
}

static inline void fat_dir_readahead(struct inode *dir, sector_t iblock,
                             sector_t phys)
{
      struct super_block *sb = dir->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bh;
      int sec;

      /* This is not a first sector of cluster, or sec_per_clus == 1 */
      if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
            return;
      /* root dir of FAT12/FAT16 */
      if ((sbi->fat_bits != 32) && (dir->i_ino == MSDOS_ROOT_INO))
            return;

      bh = sb_find_get_block(sb, phys);
      if (bh == NULL || !buffer_uptodate(bh)) {
            for (sec = 0; sec < sbi->sec_per_clus; sec++)
                  sb_breadahead(sb, phys + sec);
      }
      brelse(bh);
}

/* Returns the inode number of the directory entry at offset pos. If bh is
   non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
   returned in bh.
   AV. Most often we do it item-by-item. Makes sense to optimize.
   AV. OK, there we go: if both bh and de are non-NULL we assume that we just
   AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
   AV. It's done in fat_get_entry() (inlined), here the slow case lives.
   AV. Additionally, when we return -1 (i.e. reached the end of directory)
   AV. we make bh NULL.
 */
static int fat__get_entry(struct inode *dir, loff_t *pos,
                    struct buffer_head **bh, struct msdos_dir_entry **de)
{
      struct super_block *sb = dir->i_sb;
      sector_t phys, iblock;
      unsigned long mapped_blocks;
      int err, offset;

next:
      if (*bh)
            brelse(*bh);

      *bh = NULL;
      iblock = *pos >> sb->s_blocksize_bits;
      err = fat_bmap(dir, iblock, &phys, &mapped_blocks);
      if (err || !phys)
            return -1;  /* beyond EOF or error */

      fat_dir_readahead(dir, iblock, phys);

      *bh = sb_bread(sb, phys);
      if (*bh == NULL) {
            printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
                   (unsigned long long)phys);
            /* skip this block */
            *pos = (iblock + 1) << sb->s_blocksize_bits;
            goto next;
      }

      offset = *pos & (sb->s_blocksize - 1);
      *pos += sizeof(struct msdos_dir_entry);
      *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);

      return 0;
}

static inline int fat_get_entry(struct inode *dir, loff_t *pos,
                        struct buffer_head **bh,
                        struct msdos_dir_entry **de)
{
      /* Fast stuff first */
      if (*bh && *de &&
          (*de - (struct msdos_dir_entry *)(*bh)->b_data) < MSDOS_SB(dir->i_sb)->dir_per_block - 1) {
            *pos += sizeof(struct msdos_dir_entry);
            (*de)++;
            return 0;
      }
      return fat__get_entry(dir, pos, bh, de);
}

/*
 * Convert Unicode 16 to UTF-8, translated Unicode, or ASCII.
 * If uni_xlate is enabled and we can't get a 1:1 conversion, use a
 * colon as an escape character since it is normally invalid on the vfat
 * filesystem. The following four characters are the hexadecimal digits
 * of Unicode value. This lets us do a full dump and restore of Unicode
 * filenames. We could get into some trouble with long Unicode names,
 * but ignore that right now.
 * Ahem... Stack smashing in ring 0 isn't fun. Fixed.
 */
static int uni16_to_x8(unsigned char *ascii, wchar_t *uni, int uni_xlate,
                   struct nls_table *nls)
{
      wchar_t *ip, ec;
      unsigned char *op, nc;
      int charlen;
      int k;

      ip = uni;
      op = ascii;

      while (*ip) {
            ec = *ip++;
            if ( (charlen = nls->uni2char(ec, op, NLS_MAX_CHARSET_SIZE)) > 0) {
                  op += charlen;
            } else {
                  if (uni_xlate == 1) {
                        *op = ':';
                        for (k = 4; k > 0; k--) {
                              nc = ec & 0xF;
                              op[k] = nc > 9    ? nc + ('a' - 10)
                                          : nc + '0';
                              ec >>= 4;
                        }
                        op += 5;
                  } else {
                        *op++ = '?';
                  }
            }
            /* We have some slack there, so it's OK */
            if (op>ascii+256) {
                  op = ascii + 256;
                  break;
            }
      }
      *op = 0;
      return (op - ascii);
}

static inline int
fat_short2uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
{
      int charlen;

      charlen = t->char2uni(c, clen, uni);
      if (charlen < 0) {
            *uni = 0x003f;    /* a question mark */
            charlen = 1;
      }
      return charlen;
}

static inline int
fat_short2lower_uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
{
      int charlen;
      wchar_t wc;

      charlen = t->char2uni(c, clen, &wc);
      if (charlen < 0) {
            *uni = 0x003f;    /* a question mark */
            charlen = 1;
      } else if (charlen <= 1) {
            unsigned char nc = t->charset2lower[*c];

            if (!nc)
                  nc = *c;

            if ( (charlen = t->char2uni(&nc, 1, uni)) < 0) {
                  *uni = 0x003f;    /* a question mark */
                  charlen = 1;
            }
      } else
            *uni = wc;

      return charlen;
}

static inline int
fat_shortname2uni(struct nls_table *nls, unsigned char *buf, int buf_size,
              wchar_t *uni_buf, unsigned short opt, int lower)
{
      int len = 0;

      if (opt & VFAT_SFN_DISPLAY_LOWER)
            len =  fat_short2lower_uni(nls, buf, buf_size, uni_buf);
      else if (opt & VFAT_SFN_DISPLAY_WIN95)
            len = fat_short2uni(nls, buf, buf_size, uni_buf);
      else if (opt & VFAT_SFN_DISPLAY_WINNT) {
            if (lower)
                  len = fat_short2lower_uni(nls, buf, buf_size, uni_buf);
            else
                  len = fat_short2uni(nls, buf, buf_size, uni_buf);
      } else
            len = fat_short2uni(nls, buf, buf_size, uni_buf);

      return len;
}

enum { PARSE_INVALID = 1, PARSE_NOT_LONGNAME, PARSE_EOF, };

/**
 * fat_parse_long - Parse extended directory entry.
 *
 * This function returns zero on success, negative value on error, or one of
 * the following:
 *
 * %PARSE_INVALID - Directory entry is invalid.
 * %PARSE_NOT_LONGNAME - Directory entry does not contain longname.
 * %PARSE_EOF - Directory has no more entries.
 */
static int fat_parse_long(struct inode *dir, loff_t *pos,
                    struct buffer_head **bh, struct msdos_dir_entry **de,
                    wchar_t **unicode, unsigned char *nr_slots)
{
      struct msdos_dir_slot *ds;
      unsigned char id, slot, slots, alias_checksum;

      if (!*unicode) {
            *unicode = (wchar_t *)__get_free_page(GFP_KERNEL);
            if (!*unicode) {
                  brelse(*bh);
                  return -ENOMEM;
            }
      }
parse_long:
      slots = 0;
      ds = (struct msdos_dir_slot *)*de;
      id = ds->id;
      if (!(id & 0x40))
            return PARSE_INVALID;
      slots = id & ~0x40;
      if (slots > 20 || !slots)     /* ceil(256 * 2 / 26) */
            return PARSE_INVALID;
      *nr_slots = slots;
      alias_checksum = ds->alias_checksum;

      slot = slots;
      while (1) {
            int offset;

            slot--;
            offset = slot * 13;
            fat16_towchar(*unicode + offset, ds->name0_4, 5);
            fat16_towchar(*unicode + offset + 5, ds->name5_10, 6);
            fat16_towchar(*unicode + offset + 11, ds->name11_12, 2);

            if (ds->id & 0x40)
                  (*unicode)[offset + 13] = 0;
            if (fat_get_entry(dir, pos, bh, de) < 0)
                  return PARSE_EOF;
            if (slot == 0)
                  break;
            ds = (struct msdos_dir_slot *)*de;
            if (ds->attr != ATTR_EXT)
                  return PARSE_NOT_LONGNAME;
            if ((ds->id & ~0x40) != slot)
                  goto parse_long;
            if (ds->alias_checksum != alias_checksum)
                  goto parse_long;
      }
      if ((*de)->name[0] == DELETED_FLAG)
            return PARSE_INVALID;
      if ((*de)->attr == ATTR_EXT)
            goto parse_long;
      if (IS_FREE((*de)->name) || ((*de)->attr & ATTR_VOLUME))
            return PARSE_INVALID;
      if (fat_checksum((*de)->name) != alias_checksum)
            *nr_slots = 0;

      return 0;
}

/*
 * Return values: negative -> error, 0 -> not found, positive -> found,
 * value is the total amount of slots, including the shortname entry.
 */
int fat_search_long(struct inode *inode, const unsigned char *name,
                int name_len, struct fat_slot_info *sinfo)
{
      struct super_block *sb = inode->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bh = NULL;
      struct msdos_dir_entry *de;
      struct nls_table *nls_io = sbi->nls_io;
      struct nls_table *nls_disk = sbi->nls_disk;
      wchar_t bufuname[14];
      unsigned char xlate_len, nr_slots;
      wchar_t *unicode = NULL;
      unsigned char work[MSDOS_NAME], bufname[260];   /* 256 + 4 */
      int uni_xlate = sbi->options.unicode_xlate;
      int utf8 = sbi->options.utf8;
      int anycase = (sbi->options.name_check != 's');
      unsigned short opt_shortname = sbi->options.shortname;
      loff_t cpos = 0;
      int chl, i, j, last_u, err;

      err = -ENOENT;
      while(1) {
            if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
                  goto EODir;
parse_record:
            nr_slots = 0;
            if (de->name[0] == DELETED_FLAG)
                  continue;
            if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                  continue;
            if (de->attr != ATTR_EXT && IS_FREE(de->name))
                  continue;
            if (de->attr == ATTR_EXT) {
                  int status = fat_parse_long(inode, &cpos, &bh, &de,
                                        &unicode, &nr_slots);
                  if (status < 0)
                        return status;
                  else if (status == PARSE_INVALID)
                        continue;
                  else if (status == PARSE_NOT_LONGNAME)
                        goto parse_record;
                  else if (status == PARSE_EOF)
                        goto EODir;
            }

            memcpy(work, de->name, sizeof(de->name));
            /* see namei.c, msdos_format_name */
            if (work[0] == 0x05)
                  work[0] = 0xE5;
            for (i = 0, j = 0, last_u = 0; i < 8;) {
                  if (!work[i])
                        break;
                  chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
                                    &bufuname[j++], opt_shortname,
                                    de->lcase & CASE_LOWER_BASE);
                  if (chl <= 1) {
                        if (work[i] != ' ')
                              last_u = j;
                  } else {
                        last_u = j;
                  }
                  i += chl;
            }
            j = last_u;
            fat_short2uni(nls_disk, ".", 1, &bufuname[j++]);
            for (i = 8; i < MSDOS_NAME;) {
                  if (!work[i])
                        break;
                  chl = fat_shortname2uni(nls_disk, &work[i],
                                    MSDOS_NAME - i,
                                    &bufuname[j++], opt_shortname,
                                    de->lcase & CASE_LOWER_EXT);
                  if (chl <= 1) {
                        if (work[i] != ' ')
                              last_u = j;
                  } else {
                        last_u = j;
                  }
                  i += chl;
            }
            if (!last_u)
                  continue;

            bufuname[last_u] = 0x0000;
            xlate_len = utf8
                  ?utf8_wcstombs(bufname, bufuname, sizeof(bufname))
                  :uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
            if (xlate_len == name_len)
                  if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
                      (anycase && !nls_strnicmp(nls_io, name, bufname,
                                                xlate_len)))
                        goto Found;

            if (nr_slots) {
                  xlate_len = utf8
                        ?utf8_wcstombs(bufname, unicode, sizeof(bufname))
                        :uni16_to_x8(bufname, unicode, uni_xlate, nls_io);
                  if (xlate_len != name_len)
                        continue;
                  if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
                      (anycase && !nls_strnicmp(nls_io, name, bufname,
                                                xlate_len)))
                        goto Found;
            }
      }

Found:
      nr_slots++; /* include the de */
      sinfo->slot_off = cpos - nr_slots * sizeof(*de);
      sinfo->nr_slots = nr_slots;
      sinfo->de = de;
      sinfo->bh = bh;
      sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
      err = 0;
EODir:
      if (unicode)
            free_page((unsigned long)unicode);

      return err;
}

EXPORT_SYMBOL_GPL(fat_search_long);

struct fat_ioctl_filldir_callback {
      void __user *dirent;
      int result;
      /* for dir ioctl */
      const char *longname;
      int long_len;
      const char *shortname;
      int short_len;
};

static int __fat_readdir(struct inode *inode, struct file *filp, void *dirent,
                   filldir_t filldir, int short_only, int both)
{
      struct super_block *sb = inode->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bh;
      struct msdos_dir_entry *de;
      struct nls_table *nls_io = sbi->nls_io;
      struct nls_table *nls_disk = sbi->nls_disk;
      unsigned char long_slots;
      const char *fill_name;
      int fill_len;
      wchar_t bufuname[14];
      wchar_t *unicode = NULL;
      unsigned char c, work[MSDOS_NAME], bufname[56], *ptname = bufname;
      unsigned long lpos, dummy, *furrfu = &lpos;
      int uni_xlate = sbi->options.unicode_xlate;
      int isvfat = sbi->options.isvfat;
      int utf8 = sbi->options.utf8;
      int nocase = sbi->options.nocase;
      unsigned short opt_shortname = sbi->options.shortname;
      unsigned long inum;
      int chi, chl, i, i2, j, last, last_u, dotoffset = 0;
      loff_t cpos;
      int ret = 0;

      lock_kernel();

      cpos = filp->f_pos;
      /* Fake . and .. for the root directory. */
      if (inode->i_ino == MSDOS_ROOT_INO) {
            while (cpos < 2) {
                  if (filldir(dirent, "..", cpos+1, cpos, MSDOS_ROOT_INO, DT_DIR) < 0)
                        goto out;
                  cpos++;
                  filp->f_pos++;
            }
            if (cpos == 2) {
                  dummy = 2;
                  furrfu = &dummy;
                  cpos = 0;
            }
      }
      if (cpos & (sizeof(struct msdos_dir_entry)-1)) {
            ret = -ENOENT;
            goto out;
      }

      bh = NULL;
GetNew:
      if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
            goto EODir;
parse_record:
      long_slots = 0;
      /* Check for long filename entry */
      if (isvfat) {
            if (de->name[0] == DELETED_FLAG)
                  goto RecEnd;
            if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                  goto RecEnd;
            if (de->attr != ATTR_EXT && IS_FREE(de->name))
                  goto RecEnd;
      } else {
            if ((de->attr & ATTR_VOLUME) || IS_FREE(de->name))
                  goto RecEnd;
      }

      if (isvfat && de->attr == ATTR_EXT) {
            int status = fat_parse_long(inode, &cpos, &bh, &de,
                                  &unicode, &long_slots);
            if (status < 0) {
                  filp->f_pos = cpos;
                  ret = status;
                  goto out;
            } else if (status == PARSE_INVALID)
                  goto RecEnd;
            else if (status == PARSE_NOT_LONGNAME)
                  goto parse_record;
            else if (status == PARSE_EOF)
                  goto EODir;
      }

      if (sbi->options.dotsOK) {
            ptname = bufname;
            dotoffset = 0;
            if (de->attr & ATTR_HIDDEN) {
                  *ptname++ = '.';
                  dotoffset = 1;
            }
      }

      memcpy(work, de->name, sizeof(de->name));
      /* see namei.c, msdos_format_name */
      if (work[0] == 0x05)
            work[0] = 0xE5;
      for (i = 0, j = 0, last = 0, last_u = 0; i < 8;) {
            if (!(c = work[i]))
                  break;
            chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
                              &bufuname[j++], opt_shortname,
                              de->lcase & CASE_LOWER_BASE);
            if (chl <= 1) {
                  ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
                  if (c != ' ') {
                        last = i;
                        last_u = j;
                  }
            } else {
                  last_u = j;
                  for (chi = 0; chi < chl && i < 8; chi++) {
                        ptname[i] = work[i];
                        i++; last = i;
                  }
            }
      }
      i = last;
      j = last_u;
      fat_short2uni(nls_disk, ".", 1, &bufuname[j++]);
      ptname[i++] = '.';
      for (i2 = 8; i2 < MSDOS_NAME;) {
            if (!(c = work[i2]))
                  break;
            chl = fat_shortname2uni(nls_disk, &work[i2], MSDOS_NAME - i2,
                              &bufuname[j++], opt_shortname,
                              de->lcase & CASE_LOWER_EXT);
            if (chl <= 1) {
                  i2++;
                  ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
                  if (c != ' ') {
                        last = i;
                        last_u = j;
                  }
            } else {
                  last_u = j;
                  for (chi = 0; chi < chl && i2 < MSDOS_NAME; chi++) {
                        ptname[i++] = work[i2++];
                        last = i;
                  }
            }
      }
      if (!last)
            goto RecEnd;

      i = last + dotoffset;
      j = last_u;

      lpos = cpos - (long_slots+1)*sizeof(struct msdos_dir_entry);
      if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME))
            inum = inode->i_ino;
      else if (!memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
            inum = parent_ino(filp->f_path.dentry);
      } else {
            loff_t i_pos = fat_make_i_pos(sb, bh, de);
            struct inode *tmp = fat_iget(sb, i_pos);
            if (tmp) {
                  inum = tmp->i_ino;
                  iput(tmp);
            } else
                  inum = iunique(sb, MSDOS_ROOT_INO);
      }

      if (isvfat) {
            bufuname[j] = 0x0000;
            i = utf8 ? utf8_wcstombs(bufname, bufuname, sizeof(bufname))
                   : uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
      }

      fill_name = bufname;
      fill_len = i;
      if (!short_only && long_slots) {
            /* convert the unicode long name. 261 is maximum size
             * of unicode buffer. (13 * slots + nul) */
            void *longname = unicode + 261;
            int buf_size = PAGE_SIZE - (261 * sizeof(unicode[0]));
            int long_len = utf8
                  ? utf8_wcstombs(longname, unicode, buf_size)
                  : uni16_to_x8(longname, unicode, uni_xlate, nls_io);

            if (!both) {
                  fill_name = longname;
                  fill_len = long_len;
            } else {
                  /* hack for fat_ioctl_filldir() */
                  struct fat_ioctl_filldir_callback *p = dirent;

                  p->longname = longname;
                  p->long_len = long_len;
                  p->shortname = bufname;
                  p->short_len = i;
                  fill_name = NULL;
                  fill_len = 0;
            }
      }
      if (filldir(dirent, fill_name, fill_len, *furrfu, inum,
                (de->attr & ATTR_DIR) ? DT_DIR : DT_REG) < 0)
            goto FillFailed;

RecEnd:
      furrfu = &lpos;
      filp->f_pos = cpos;
      goto GetNew;
EODir:
      filp->f_pos = cpos;
FillFailed:
      brelse(bh);
      if (unicode)
            free_page((unsigned long)unicode);
out:
      unlock_kernel();
      return ret;
}

static int fat_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
      struct inode *inode = filp->f_path.dentry->d_inode;
      return __fat_readdir(inode, filp, dirent, filldir, 0, 0);
}

#define FAT_IOCTL_FILLDIR_FUNC(func, dirent_type)                    \
static int func(void *__buf, const char *name, int name_len,               \
                       loff_t offset, u64 ino, unsigned int d_type)  \
{                                                        \
      struct fat_ioctl_filldir_callback *buf = __buf;                \
      struct dirent_type __user *d1 = buf->dirent;                   \
      struct dirent_type __user *d2 = d1 + 1;                        \
                                                         \
      if (buf->result)                                   \
            return -EINVAL;                                    \
      buf->result++;                                           \
                                                         \
      if (name != NULL) {                                      \
            /* dirent has only short name */                   \
            if (name_len >= sizeof(d1->d_name))                \
                  name_len = sizeof(d1->d_name) - 1;           \
                                                         \
            if (put_user(0, d2->d_name)               ||       \
                put_user(0, &d2->d_reclen)                  ||       \
                copy_to_user(d1->d_name, name, name_len)    ||       \
                put_user(0, d1->d_name + name_len)          ||       \
                put_user(name_len, &d1->d_reclen))                   \
                  goto efault;                                 \
      } else {                                           \
            /* dirent has short and long name */                     \
            const char *longname = buf->longname;                    \
            int long_len = buf->long_len;                      \
            const char *shortname = buf->shortname;                  \
            int short_len = buf->short_len;                          \
                                                         \
            if (long_len >= sizeof(d1->d_name))                \
                  long_len = sizeof(d1->d_name) - 1;           \
            if (short_len >= sizeof(d1->d_name))                     \
                  short_len = sizeof(d1->d_name) - 1;          \
                                                         \
            if (copy_to_user(d2->d_name, longname, long_len)      || \
                put_user(0, d2->d_name + long_len)                || \
                put_user(long_len, &d2->d_reclen)                 || \
                put_user(ino, &d2->d_ino)                   || \
                put_user(offset, &d2->d_off)                || \
                copy_to_user(d1->d_name, shortname, short_len)    || \
                put_user(0, d1->d_name + short_len)               || \
                put_user(short_len, &d1->d_reclen))                  \
                  goto efault;                                 \
      }                                                  \
      return 0;                                          \
efault:                                                        \
      buf->result = -EFAULT;                                   \
      return -EFAULT;                                          \
}

FAT_IOCTL_FILLDIR_FUNC(fat_ioctl_filldir, dirent)

static int fat_ioctl_readdir(struct inode *inode, struct file *filp,
                       void __user *dirent, filldir_t filldir,
                       int short_only, int both)
{
      struct fat_ioctl_filldir_callback buf;
      int ret;

      buf.dirent = dirent;
      buf.result = 0;
      mutex_lock(&inode->i_mutex);
      ret = -ENOENT;
      if (!IS_DEADDIR(inode)) {
            ret = __fat_readdir(inode, filp, &buf, filldir,
                            short_only, both);
      }
      mutex_unlock(&inode->i_mutex);
      if (ret >= 0)
            ret = buf.result;
      return ret;
}

static int fat_dir_ioctl(struct inode *inode, struct file *filp,
                   unsigned int cmd, unsigned long arg)
{
      struct dirent __user *d1 = (struct dirent __user *)arg;
      int short_only, both;

      switch (cmd) {
      case VFAT_IOCTL_READDIR_SHORT:
            short_only = 1;
            both = 0;
            break;
      case VFAT_IOCTL_READDIR_BOTH:
            short_only = 0;
            both = 1;
            break;
      default:
            return fat_generic_ioctl(inode, filp, cmd, arg);
      }

      if (!access_ok(VERIFY_WRITE, d1, sizeof(struct dirent[2])))
            return -EFAULT;
      /*
       * Yes, we don't need this put_user() absolutely. However old
       * code didn't return the right value. So, app use this value,
       * in order to check whether it is EOF.
       */
      if (put_user(0, &d1->d_reclen))
            return -EFAULT;

      return fat_ioctl_readdir(inode, filp, d1, fat_ioctl_filldir,
                         short_only, both);
}

#ifdef CONFIG_COMPAT
#define     VFAT_IOCTL_READDIR_BOTH32     _IOR('r', 1, struct compat_dirent[2])
#define     VFAT_IOCTL_READDIR_SHORT32    _IOR('r', 2, struct compat_dirent[2])

FAT_IOCTL_FILLDIR_FUNC(fat_compat_ioctl_filldir, compat_dirent)

static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
                         unsigned long arg)
{
      struct inode *inode = filp->f_path.dentry->d_inode;
      struct compat_dirent __user *d1 = compat_ptr(arg);
      int short_only, both;

      switch (cmd) {
      case VFAT_IOCTL_READDIR_SHORT32:
            short_only = 1;
            both = 0;
            break;
      case VFAT_IOCTL_READDIR_BOTH32:
            short_only = 0;
            both = 1;
            break;
      default:
            return -ENOIOCTLCMD;
      }

      if (!access_ok(VERIFY_WRITE, d1, sizeof(struct compat_dirent[2])))
            return -EFAULT;
      /*
       * Yes, we don't need this put_user() absolutely. However old
       * code didn't return the right value. So, app use this value,
       * in order to check whether it is EOF.
       */
      if (put_user(0, &d1->d_reclen))
            return -EFAULT;

      return fat_ioctl_readdir(inode, filp, d1, fat_compat_ioctl_filldir,
                         short_only, both);
}
#endif /* CONFIG_COMPAT */

const struct file_operations fat_dir_operations = {
      .read       = generic_read_dir,
      .readdir    = fat_readdir,
      .ioctl            = fat_dir_ioctl,
#ifdef CONFIG_COMPAT
      .compat_ioctl     = fat_compat_dir_ioctl,
#endif
      .fsync            = file_fsync,
};

static int fat_get_short_entry(struct inode *dir, loff_t *pos,
                         struct buffer_head **bh,
                         struct msdos_dir_entry **de)
{
      while (fat_get_entry(dir, pos, bh, de) >= 0) {
            /* free entry or long name entry or volume label */
            if (!IS_FREE((*de)->name) && !((*de)->attr & ATTR_VOLUME))
                  return 0;
      }
      return -ENOENT;
}

/*
 * The ".." entry can not provide the "struct fat_slot_info" informations
 * for inode. So, this function provide the some informations only.
 */
int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
                   struct msdos_dir_entry **de, loff_t *i_pos)
{
      loff_t offset;

      offset = 0;
      *bh = NULL;
      while (fat_get_short_entry(dir, &offset, bh, de) >= 0) {
            if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                  *i_pos = fat_make_i_pos(dir->i_sb, *bh, *de);
                  return 0;
            }
      }
      return -ENOENT;
}

EXPORT_SYMBOL_GPL(fat_get_dotdot_entry);

/* See if directory is empty */
int fat_dir_empty(struct inode *dir)
{
      struct buffer_head *bh;
      struct msdos_dir_entry *de;
      loff_t cpos;
      int result = 0;

      bh = NULL;
      cpos = 0;
      while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
            if (strncmp(de->name, MSDOS_DOT   , MSDOS_NAME) &&
                strncmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                  result = -ENOTEMPTY;
                  break;
            }
      }
      brelse(bh);
      return result;
}

EXPORT_SYMBOL_GPL(fat_dir_empty);

/*
 * fat_subdirs counts the number of sub-directories of dir. It can be run
 * on directories being created.
 */
int fat_subdirs(struct inode *dir)
{
      struct buffer_head *bh;
      struct msdos_dir_entry *de;
      loff_t cpos;
      int count = 0;

      bh = NULL;
      cpos = 0;
      while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
            if (de->attr & ATTR_DIR)
                  count++;
      }
      brelse(bh);
      return count;
}

/*
 * Scans a directory for a given file (name points to its formatted name).
 * Returns an error code or zero.
 */
int fat_scan(struct inode *dir, const unsigned char *name,
           struct fat_slot_info *sinfo)
{
      struct super_block *sb = dir->i_sb;

      sinfo->slot_off = 0;
      sinfo->bh = NULL;
      while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
                           &sinfo->de) >= 0) {
            if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
                  sinfo->slot_off -= sizeof(*sinfo->de);
                  sinfo->nr_slots = 1;
                  sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
                  return 0;
            }
      }
      return -ENOENT;
}

EXPORT_SYMBOL_GPL(fat_scan);

static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
{
      struct super_block *sb = dir->i_sb;
      struct buffer_head *bh;
      struct msdos_dir_entry *de, *endp;
      int err = 0, orig_slots;

      while (nr_slots) {
            bh = NULL;
            if (fat_get_entry(dir, &pos, &bh, &de) < 0) {
                  err = -EIO;
                  break;
            }

            orig_slots = nr_slots;
            endp = (struct msdos_dir_entry *)(bh->b_data + sb->s_blocksize);
            while (nr_slots && de < endp) {
                  de->name[0] = DELETED_FLAG;
                  de++;
                  nr_slots--;
            }
            mark_buffer_dirty(bh);
            if (IS_DIRSYNC(dir))
                  err = sync_dirty_buffer(bh);
            brelse(bh);
            if (err)
                  break;

            /* pos is *next* de's position, so this does `- sizeof(de)' */
            pos += ((orig_slots - nr_slots) * sizeof(*de)) - sizeof(*de);
      }

      return err;
}

int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
{
      struct msdos_dir_entry *de;
      struct buffer_head *bh;
      int err = 0, nr_slots;

      /*
       * First stage: Remove the shortname. By this, the directory
       * entry is removed.
       */
      nr_slots = sinfo->nr_slots;
      de = sinfo->de;
      sinfo->de = NULL;
      bh = sinfo->bh;
      sinfo->bh = NULL;
      while (nr_slots && de >= (struct msdos_dir_entry *)bh->b_data) {
            de->name[0] = DELETED_FLAG;
            de--;
            nr_slots--;
      }
      mark_buffer_dirty(bh);
      if (IS_DIRSYNC(dir))
            err = sync_dirty_buffer(bh);
      brelse(bh);
      if (err)
            return err;
      dir->i_version++;

      if (nr_slots) {
            /*
             * Second stage: remove the remaining longname slots.
             * (This directory entry is already removed, and so return
             * the success)
             */
            err = __fat_remove_entries(dir, sinfo->slot_off, nr_slots);
            if (err) {
                  printk(KERN_WARNING
                         "FAT: Couldn't remove the long name slots\n");
            }
      }

      dir->i_mtime = dir->i_atime = CURRENT_TIME_SEC;
      if (IS_DIRSYNC(dir))
            (void)fat_sync_inode(dir);
      else
            mark_inode_dirty(dir);

      return 0;
}

EXPORT_SYMBOL_GPL(fat_remove_entries);

static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
                        struct buffer_head **bhs, int nr_bhs)
{
      struct super_block *sb = dir->i_sb;
      sector_t last_blknr = blknr + MSDOS_SB(sb)->sec_per_clus;
      int err, i, n;

      /* Zeroing the unused blocks on this cluster */
      blknr += nr_used;
      n = nr_used;
      while (blknr < last_blknr) {
            bhs[n] = sb_getblk(sb, blknr);
            if (!bhs[n]) {
                  err = -ENOMEM;
                  goto error;
            }
            memset(bhs[n]->b_data, 0, sb->s_blocksize);
            set_buffer_uptodate(bhs[n]);
            mark_buffer_dirty(bhs[n]);

            n++;
            blknr++;
            if (n == nr_bhs) {
                  if (IS_DIRSYNC(dir)) {
                        err = fat_sync_bhs(bhs, n);
                        if (err)
                              goto error;
                  }
                  for (i = 0; i < n; i++)
                        brelse(bhs[i]);
                  n = 0;
            }
      }
      if (IS_DIRSYNC(dir)) {
            err = fat_sync_bhs(bhs, n);
            if (err)
                  goto error;
      }
      for (i = 0; i < n; i++)
            brelse(bhs[i]);

      return 0;

error:
      for (i = 0; i < n; i++)
            bforget(bhs[i]);
      return err;
}

int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
{
      struct super_block *sb = dir->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bhs[MAX_BUF_PER_PAGE];
      struct msdos_dir_entry *de;
      sector_t blknr;
      __le16 date, time;
      int err, cluster;

      err = fat_alloc_clusters(dir, &cluster, 1);
      if (err)
            goto error;

      blknr = fat_clus_to_blknr(sbi, cluster);
      bhs[0] = sb_getblk(sb, blknr);
      if (!bhs[0]) {
            err = -ENOMEM;
            goto error_free;
      }

      fat_date_unix2dos(ts->tv_sec, &time, &date);

      de = (struct msdos_dir_entry *)bhs[0]->b_data;
      /* filling the new directory slots ("." and ".." entries) */
      memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
      memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
      de->attr = de[1].attr = ATTR_DIR;
      de[0].lcase = de[1].lcase = 0;
      de[0].time = de[1].time = time;
      de[0].date = de[1].date = date;
      de[0].ctime_cs = de[1].ctime_cs = 0;
      if (sbi->options.isvfat) {
            /* extra timestamps */
            de[0].ctime = de[1].ctime = time;
            de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
      } else {
            de[0].ctime = de[1].ctime = 0;
            de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
      }
      de[0].start = cpu_to_le16(cluster);
      de[0].starthi = cpu_to_le16(cluster >> 16);
      de[1].start = cpu_to_le16(MSDOS_I(dir)->i_logstart);
      de[1].starthi = cpu_to_le16(MSDOS_I(dir)->i_logstart >> 16);
      de[0].size = de[1].size = 0;
      memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
      set_buffer_uptodate(bhs[0]);
      mark_buffer_dirty(bhs[0]);

      err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
      if (err)
            goto error_free;

      return cluster;

error_free:
      fat_free_clusters(dir, cluster);
error:
      return err;
}

EXPORT_SYMBOL_GPL(fat_alloc_new_dir);

static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
                         int *nr_cluster, struct msdos_dir_entry **de,
                         struct buffer_head **bh, loff_t *i_pos)
{
      struct super_block *sb = dir->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bhs[MAX_BUF_PER_PAGE];
      sector_t blknr, start_blknr, last_blknr;
      unsigned long size, copy;
      int err, i, n, offset, cluster[2];

      /*
       * The minimum cluster size is 512bytes, and maximum entry
       * size is 32*slots (672bytes).  So, iff the cluster size is
       * 512bytes, we may need two clusters.
       */
      size = nr_slots * sizeof(struct msdos_dir_entry);
      *nr_cluster = (size + (sbi->cluster_size - 1)) >> sbi->cluster_bits;
      BUG_ON(*nr_cluster > 2);

      err = fat_alloc_clusters(dir, cluster, *nr_cluster);
      if (err)
            goto error;

      /*
       * First stage: Fill the directory entry.  NOTE: This cluster
       * is not referenced from any inode yet, so updates order is
       * not important.
       */
      i = n = copy = 0;
      do {
            start_blknr = blknr = fat_clus_to_blknr(sbi, cluster[i]);
            last_blknr = start_blknr + sbi->sec_per_clus;
            while (blknr < last_blknr) {
                  bhs[n] = sb_getblk(sb, blknr);
                  if (!bhs[n]) {
                        err = -ENOMEM;
                        goto error_nomem;
                  }

                  /* fill the directory entry */
                  copy = min(size, sb->s_blocksize);
                  memcpy(bhs[n]->b_data, slots, copy);
                  slots += copy;
                  size -= copy;
                  set_buffer_uptodate(bhs[n]);
                  mark_buffer_dirty(bhs[n]);
                  if (!size)
                        break;
                  n++;
                  blknr++;
            }
      } while (++i < *nr_cluster);

      memset(bhs[n]->b_data + copy, 0, sb->s_blocksize - copy);
      offset = copy - sizeof(struct msdos_dir_entry);
      get_bh(bhs[n]);
      *bh = bhs[n];
      *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
      *i_pos = fat_make_i_pos(sb, *bh, *de);

      /* Second stage: clear the rest of cluster, and write outs */
      err = fat_zeroed_cluster(dir, start_blknr, ++n, bhs, MAX_BUF_PER_PAGE);
      if (err)
            goto error_free;

      return cluster[0];

error_free:
      brelse(*bh);
      *bh = NULL;
      n = 0;
error_nomem:
      for (i = 0; i < n; i++)
            bforget(bhs[i]);
      fat_free_clusters(dir, cluster[0]);
error:
      return err;
}

int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
                struct fat_slot_info *sinfo)
{
      struct super_block *sb = dir->i_sb;
      struct msdos_sb_info *sbi = MSDOS_SB(sb);
      struct buffer_head *bh, *prev, *bhs[3]; /* 32*slots (672bytes) */
      struct msdos_dir_entry *de;
      int err, free_slots, i, nr_bhs;
      loff_t pos, i_pos;

      sinfo->nr_slots = nr_slots;

      /* First stage: search free direcotry entries */
      free_slots = nr_bhs = 0;
      bh = prev = NULL;
      pos = 0;
      err = -ENOSPC;
      while (fat_get_entry(dir, &pos, &bh, &de) > -1) {
            /* check the maximum size of directory */
            if (pos >= FAT_MAX_DIR_SIZE)
                  goto error;

            if (IS_FREE(de->name)) {
                  if (prev != bh) {
                        get_bh(bh);
                        bhs[nr_bhs] = prev = bh;
                        nr_bhs++;
                  }
                  free_slots++;
                  if (free_slots == nr_slots)
                        goto found;
            } else {
                  for (i = 0; i < nr_bhs; i++)
                        brelse(bhs[i]);
                  prev = NULL;
                  free_slots = nr_bhs = 0;
            }
      }
      if (dir->i_ino == MSDOS_ROOT_INO) {
            if (sbi->fat_bits != 32)
                  goto error;
      } else if (MSDOS_I(dir)->i_start == 0) {
            printk(KERN_ERR "FAT: Corrupted directory (i_pos %lld)\n",
                   MSDOS_I(dir)->i_pos);
            err = -EIO;
            goto error;
      }

found:
      err = 0;
      pos -= free_slots * sizeof(*de);
      nr_slots -= free_slots;
      if (free_slots) {
            /*
             * Second stage: filling the free entries with new entries.
             * NOTE: If this slots has shortname, first, we write
             * the long name slots, then write the short name.
             */
            int size = free_slots * sizeof(*de);
            int offset = pos & (sb->s_blocksize - 1);
            int long_bhs = nr_bhs - (nr_slots == 0);

            /* Fill the long name slots. */
            for (i = 0; i < long_bhs; i++) {
                  int copy = min_t(int, sb->s_blocksize - offset, size);
                  memcpy(bhs[i]->b_data + offset, slots, copy);
                  mark_buffer_dirty(bhs[i]);
                  offset = 0;
                  slots += copy;
                  size -= copy;
            }
            if (long_bhs && IS_DIRSYNC(dir))
                  err = fat_sync_bhs(bhs, long_bhs);
            if (!err && i < nr_bhs) {
                  /* Fill the short name slot. */
                  int copy = min_t(int, sb->s_blocksize - offset, size);
                  memcpy(bhs[i]->b_data + offset, slots, copy);
                  mark_buffer_dirty(bhs[i]);
                  if (IS_DIRSYNC(dir))
                        err = sync_dirty_buffer(bhs[i]);
            }
            for (i = 0; i < nr_bhs; i++)
                  brelse(bhs[i]);
            if (err)
                  goto error_remove;
      }

      if (nr_slots) {
            int cluster, nr_cluster;

            /*
             * Third stage: allocate the cluster for new entries.
             * And initialize the cluster with new entries, then
             * add the cluster to dir.
             */
            cluster = fat_add_new_entries(dir, slots, nr_slots, &nr_cluster,
                                    &de, &bh, &i_pos);
            if (cluster < 0) {
                  err = cluster;
                  goto error_remove;
            }
            err = fat_chain_add(dir, cluster, nr_cluster);
            if (err) {
                  fat_free_clusters(dir, cluster);
                  goto error_remove;
            }
            if (dir->i_size & (sbi->cluster_size - 1)) {
                  fat_fs_panic(sb, "Odd directory size");
                  dir->i_size = (dir->i_size + sbi->cluster_size - 1)
                        & ~((loff_t)sbi->cluster_size - 1);
            }
            dir->i_size += nr_cluster << sbi->cluster_bits;
            MSDOS_I(dir)->mmu_private += nr_cluster << sbi->cluster_bits;
      }
      sinfo->slot_off = pos;
      sinfo->de = de;
      sinfo->bh = bh;
      sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);

      return 0;

error:
      brelse(bh);
      for (i = 0; i < nr_bhs; i++)
            brelse(bhs[i]);
      return err;

error_remove:
      brelse(bh);
      if (free_slots)
            __fat_remove_entries(dir, pos, free_slots);
      return err;
}

EXPORT_SYMBOL_GPL(fat_add_entries);

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